Butterfly, one passing over (7)
I believe the answer is:
skipper
This clue might be a double definition.
'butterfly' is the first definition.
Although both the answer and definition are singular nouns, I cannot understand how they can define each other.
'one passing over' is the second definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
Can you help me to learn more?
(Other definitions for skipper that I've seen before include "one that's put over the side" , "sleep in outhouse" , "One who misses" , "sea-captain" , "Shakespeare's giddy youth" .)